This relates generally to electronic devices and, more particularly, to electronic devices with displays.
Electronic devices often include displays. For example, cellular telephones and computers have displays.
Displays such as liquid crystal displays have arrays of display pixels. Display driver circuitry is used to display images on a display by loading image data into an array of display pixels. To enhance visibility of the images on a display, the display may be provided with a backlight unit. The backlight unit emits backlight that passes through the array of display pixels and illuminates the images that are being displayed.
The dynamic range of a display may be enhanced by using a backlight unit that is capable of localized dimming. This type of backlight unit has an array of light-emitting diodes spread across the display. In portions of the display in which bright image content is being displayed, the light-emitting diodes are driven and supply backlight. In portions of the display in which black image content is being displayed, the light-emitting diodes can be turned off to ensure that the display appears completely black.
It can be challenging to implement a backlight unit with local dimming capabilities in a display. If care is not taken, the circuitry used to drive the array of light-emitting diodes can be overly complex. Drive circuit complexity can be reduced by using fewer light-emitting diodes in the display, but the lowered backlight resolution that results from this type of approach can give rise to undesired visible artifacts such as halos around bright portions of an image that are set against dark backgrounds.
It would therefore be desirable to be able to provide improved backlighting for a display.